This invention relates to apparatus for and a method of simultaneously axially inserting the windings of a multiple pole, multiple phase electric motor or other dynamoelectric machine into the radial slots of its stator core.
Generally, a stator for an electric motor or other dynamoelectric machine comprises a stack of pre-punched laminations of a suitable ferromagnetic sheet material forming the stator core. Each of the laminations has a central opening therein with a plurality of radially extending teeth spaced at equal angular intervals defining a plurality of radially extending slots between the teeth. Typically, the inner ends of the teeth are part-circular so as to define a central bore for the stator. In an electric motor, windings, comprising coils of copper magnet wire coated with a suitable varnish electrical insulation material, are inserted into the slots in a desired arrangement so as to generate a desired magnetic flux field when energized. The portions of the coils extending over the end faces of the motors between the slots receiving the coils are referred to as end turns.
In recent years, the coils constituting the windings of the stator have been inserted into the stator by means of axially operable coil assembling apparatus, such as is illustrated in U.S. Pat. No. 3,324,536, granted to Donald E. Hill on June 13, 1967. With such axially operable coil assembling apparatus, pre-wound coils are placed over a circular array of spaced fingers, with one of the fingers being in register with a respective tooth of a stator, and with portions of the pre-wound coils spanning between the fingers and constituting coil chord segments. Then the stator is installed on the upper ends of the fingers with the teeth of the stator in radial register with the fingers and with the stator being fixedly held in place by suitable clamp means. Then, an axially movable ram is actuated so as to move a stripper axially (outwardly) within the circular array of fingers such that the outer face of the stripper engages the chord segments of the coils placed on and spanning between the fingers, and such that the stripper pushes the chord segments upwardly and causes the side portions of each of the coils to "flow" through the gaps between the fingers and to be laid within their respective slots of the stator core. The ram continues to advance to its fully extended position such that the side portions of the coils are fully inserted into their respective slots, such that the chord segments initially spanning between the fingers constitute the end turns of the windings at the upper end face of the stator core, and such that the end portions of the coils opposite the chord segments constitute the end turns of the winding at the opposite end face of the stator core. The slots of the stator are often provided with suitable plastic insulators so as to electrically insulate the windings from the stator and to protect the windings from abrasion on the stator as they are inserted into the slots. In the manner disclosed in the above-noted U.S. Pat. No. 3,324,536, insulative wedges of suitable plastic sheet material may be inserted into the slots after the coils have been inserted by means of the axial coil inserter so as to hold the coils in place.
While such axial coil inserting apparatus have worked well for their intended purposes, there have been long-standing problems, particularly with regard to inserting the windings for multiple pole, multiple phase electric motors, or for other windings in which the chord segments of the coils are axially overlapped with one another after they have been placed on the fingers. For example, in a two-pole, three-phase motor, six different coil groups or coil sets must be inserted into the slots of the stator such that the six coil groups constitute the poles for the windings. Typically, these coils groups are arranged in three pairs, with each coil group of each pair being diametrically opposed to its respective pair member, and with each of the three pairs being angularly offset with regard to the next adjacent coil group pair by an angle of about 120 degrees. In this manner, the chord segments of the coils of each of the coil groups placed on the axial fingers of the coil inserter extend across the circular opening between the fingers cross and axially overlie or overlap one another.
Upon inserting the windings of such multiple pole, multiple phase electric motors, as hereabove described, utilizing the coil assembling apparatus, as shown in U.S. Pat. No. 3,324,526, problems were encountered in that the stripper of the coil inserting apparatus would first engage the lowermost chord segments of the lowermost pair of coil groups positioned on the fingers such that upon axial advancement of the stripper, and the chord segments of lowermost pair of coil groups would be forced into the chord segments of the upper coil groups. Thus, this lowermost pair of coil groups must exert sufficient axial force on the other coil groups to effect axial movement of all of the coil groups relative to the stator so as to cause them to move axially with respect to the fingers and to the stator for being laid in their respective stator slots. However, this resulted in the application of excessive force to at least certain of the wires comprising the various coils, which resulted in undue stretching and abrading of the magnet wire, with the consequent deformation of the magnet wire and loss of the electrical insulation therefrom.
To overcome these long-standing problems, such multiple pole, multiple phase windings for electric motors were often axially inserted into the stator in steps. First, a first pair of coil groups would be placed on the fingers, with each of the coil groups being diametrically opposed to one another such that the chord segments extending between the fingers did not axially overlap with one another. The stator would then be inserted onto the fingers and clamped in place. Then, the stripper would be advanced so as to insert this first pair of coil groups into their respective slots. Then, the stator would be removed, a second pair of coil groups would be placed onto their respective fingers, the stator would be inserted on the fingers and clamped in place, and the stripper would be advanced thereby to insert this second pair of coil groups into their respective slots. This procedure would be repeated until all of the pairs of coil groups were properly inserted into their respective slots. While this method of inserting multiple pole windings for a multiple pole, multiple phase motor could be done with coil assembling apparatus, generally as shown in the above-noted U.S. Pat. No. 3,324,536, it required separate placements of the pairs of coil groups for the different phases in the stator. In order to insert the windings of a two pole, three phase motor, three separate insertion steps were required.
It will be appreciated that the separate placement of each of the pairs of coil groups in the stator required substantial additional labor, and thus substantially increased the cost of the three-phase stator assembly.
There has been a long-standing need for an axial coil inserting apparatus and a method which permitted the coil groups for multiple pole, multiple phase windings to be simultaneously inserted into the slots of the stator in one operation.